Which sample has the most molecules?

Four gases are weighed out, $10.0$ g of each. You will write a function for the molar mass from the formula, a function for the number of molecules, and then find the sample with the most molecules.

The idea. $M$ is the sum of the atomic masses in the formula, $n = \dfrac{m}{M}$ and $N = n \times N_A$.

Your tasks.

1. In molar_mass, return the molar mass in g/mol from the dictionary of atoms and their counts.
2. In molecules, return the number of molecules in the sample.
3. Set most to the name of the sample with the most molecules.